"The Outside Track" is in the edition of "In the Days When the World was Wide" which I have, in between "Second Class Wait Here" and "The Storm that is to Come". That's the "Collected Poetical Works" version originally published back in 1925. (My edition is quite a bit later!)

Great song. And in the way a lot of the best songs are, it's at the same time very specific to a particular situation (a mate heading off to a distant country) and applicable to a whole lot of different situations - as the chorus goes, "they marry and vanish and die".